Method of separating hydrocarbons from3or4

 

(57) Abstract:

The invention relates to the separation of mixtures of lower hydrocarbons. For the separation of mixtures of hydrocarbons WITH3or4apply extractive distillation in the presence of high-boiling polar agent. Less saturated hydrocarbons are separated from the extractant in the distant distillation zone where there is an auxiliary desorption agent in the amount of 2 to 35 wt.%. As a desorption agent using a hydrocarbon and/or ether, which have a normal boiling point at 30-85oWith higher than target desormiere hydrocarbons. Part of the desorption agent output flow of the extractant followed by Stripping it from the extractant in an additional column operating at lower pressure, preferably close to atmospheric, or part of the desorption agent output flow target debarbieux hydrocarbons with subsequent separation of the mixture by distillation. It is possible to output desorption agent simultaneously with the flow of the extractant and flow of the target hydrocarbons. Preferably the flow allocated desorption agent return in the condensed state in the middle or lower part and/geticheskie costs separation of hydrocarbons. 7 C.p. f-crystals, 3 ill., table 2.

The invention relates to the field of separation bizcochada hydrocarbons of varying degrees of unsaturation.

More specifically the invention relates to the field of separation of hydrocarbon, C3or C4extractive distillation in the presence of high-boiling polar extractants.

There is a method of separation bizcochada hydrocarbons of varying degrees of unsaturation (propane and propene, butane and butenes, butenes and butadiene, pentane and pentanol, pentanol and pentadiene and so on) by extractive distillation in the presence of high-boiling polar extractants: N,N-dimethylformamide. N, N-dimethylacetamide, N-methylpyrrolidone, acetonitrile, methoxypropionitrile or mixtures thereof. (P. A. Kirpichnikov and other Album of technological schemes of the main industries of synthetic rubber, L., Chemistry, 1986, S. 14-17, 23-45).

When using high-boiling extractants there are serious difficulties with the desorption of these hydrocarbons, if the boiling point of the extracting agent 100 or moreoC higher than that debarbieux hydrocarbons. Economically feasible to use for condensation of decorate industrial circulating water, allow the UB>4at the same temperature (40o) must be maintained from the top of desorber high pressure, for example by condensation of propene 16 ATA, isobutene - 4,6 ATA, 1,3-butadiene - 4,4 ATA. However, taking into account gas dynamic resistance, the pressure in the cube in the first case, respectively 16,3-17,0, in the second and third cases - 4,8-5,5 ATA. At these pressures the boiling point of concentrated polar extractants hypothetically would be: dimethylformamide 299o(when desorption of hydrocarbons, C3) and 241o(when desorption of C4), dimethylacetamide, respectively 308oC and 242oC and so on), but they are practically impossible due to decomposition of the extractants.

The problem in the industry decide by desorption at a lower (than in the extractive distillation column) pressure, usually close to atmospheric, and carry out the condensation of decorate with special dealbata (for example, cooled to - 20 - -30obrine) or by compressing the output of desorber steam flow with subsequent condensation of industrial circulating water.

Both are very bogoroditsye and require additional kapitalanlage when using polar organic solvents with water. However, when the above pressures, the temperature in the cube desorption column remains very high and there is significant hydrolysis of the polar organic solvent.

We propose a method of separating hydrocarbons FROM3or4extractive distillation in the presence of high-boiling polar agent with subsequent distillation of the less saturated(s) of hydrocarbon(s) from the extractant and recycling of the extractant in the upper part of the extractive distillation zone, which consists in the fact that the Department less saturated hydrocarbons carried out at least in two distant areas, in Cuba, the first of which supports the concentration of 2-35%, preferably 3-35% auxiliary desorption agent - hydrocarbon(s) and/or simple(s), ether(s), with(their) normal boiling point at 30-85ohigher than the target desormiere hydrocarbons, and the specified desorption agent at least partially derive from the flow of extractant followed by Stripping it from the extractant in an additional column operating at lower pressure, preferably close to atmospheric, or/and output flow target debarbieux hydrocarbons, which are then distilled off from JASS is most of the extractant and the target debarbieux hydrocarbon stream, mainly containing desorption agent, return in the condensed state in the middle and/or bottom and/or cube extractive distillation column and/or the first remote areas.

As a variant of the proposed method lies in the fact that at the conclusion desorption agent with a stream of the target debarbieux hydrocarbons in the first pasture area maintains the pressure at least 1 bar lower than in the area of extractive distillation.

As a variant it is also proposed a method lies in the fact that as the extractant used aprotic solvents selected from the group comprising N,N-dimethylformamide, N,N-dimethylacetamide, N-organic N-formylmorpholine - methoxypropionitrile, acetonitrile or mixtures thereof with water and/or inhibitors of polymerization of hydrocarbons and/or inhibitors of the hydrolysis of the polar solvent and corrosion.

As a variant of the proposed method lies in the fact that the target deformiruemym stream is a stream containing predominantly 1,3-butadiene, and desorption agent is hydrocarbon(s) and/or ethers, C5or/and C6for example pentane or/and hexane and/or methyl tert-butyl ether.

As varisty zone extractive distillation and/or served in the original partial hydrocarbon mixtures.

As a variant of the proposed method lies in the fact that the separation of mixtures containing 1,3-butadiene and/or PROPADIENE and/or acetylene C3-C4in the composition of the extractant enter at least nitrite (s) and/or nitrosoguanidine(I).

As a variant of the proposed method lies in the fact that in the lower part and/or the heater and/or a cube column extractive distillation return a stream containing predominantly target desormiere hydrocarbons.

In the formula, and the description of the invention, the expression "high-boiling polar solvent" is understood not only as individual substances (dimethylformamide, dimethylacetamide, acetonitrile), but also as a high-boiling mixtures of substances, in which prevails(ut) polar(s) organic substance(s) and may contain water and a small amount of hydrocarbons, inhibitors of thermopolymerization, corrosion, and other special additives and impurities.

Zone extractive distillation, distillation, Stripping and distillation and desorption understood not necessarily as a specific individual devices. Zones can be combined in a single column apparatus or, on the contrary, some of the zones, such as the extractive distillation zone, could conruyt as a single area.

Part of the input heavier ("desorbers") hydrocarbons and/or esters can be left in the extractant and filed in its composition in the upper part of the extractive distillation zone.

The method is illustrated in the drawings 1-3 and examples 1-5. These drawings and examples do not exhaust all possible options for the use of the invention and possible other solutions, while respecting the fact set forth in the claims.

According Fig. 1, a partial mixture flow 1 served in the middle part of the extractive distillation column K-1. In the upper part of the K-1 serves extractant (stream 2). Top-To-1 output distillate D1 (stream 3), containing mainly saturated hydrocarbons. Bottom-To-1 output stream 4 containing at least extractant and less saturated hydrocarbons, which are referred to column K-2.

To reduce the temperature in the lower part and/or cube K-1 column can be sent to a stream containing predominantly target desormiere components (dashed line).

Top K-2 output stream decorate D2 (stream 5), mainly containing the target product.

In the lower and/or middle portion and/or the cube of the column K-2 or/and the lower part and/or cube columns viraemia hydrocarbons) normal boiling point (threads 6 and 6'). From below By-2 output stream 7 containing the extractant and desorption agent sent to more distant machine (desorber) K-3 working with less than K-2, pressure.

Top-To-3 output steam flow containing predominantly desorption agent, which after condensation return in the middle and/or bottom and/or cube column K-2 or/and the lower part and/or cube K-1 column.

Bottom-To-3 output stream of the extractant, which is directed into the upper part of column K-1.

According Fig. 2, the flow decorate D2, containing predominantly allocated target product, is removed as a side stream column K-1 (flow 5). In the future it can be subjected to further distillation from the desorption agent and/or extractant.

In the lower part and/or the cube column K-1 direct stream 6 containing desorption agent. Stream 4 containing the extractant and desorption agent, sent to more distant machine (desorber) K-2, operating at less than K-1, pressure.

Top K-2 output stream containing predominantly desorption agent, which condense and return to the lower part and/or cube K-1. From below By-2 output stream of the extractant, the emitted hydrocarbons and, perhaps desorption agent, refer to the column K-2. From the bottom of column K-2 output stream and, mainly containing the extractant and possibly partially desorption agent that is directed to the upper part of column K-1.

Top K-2 output stream 5 containing mainly target allocated hydrocarbons and desorption agent.

Stream 5 is sent to the column K-3, where they perform branch target allocated hydrocarbons (stream 6) from a stream containing predominantly desorption agent (stream 7), which return in the middle and/or bottom and/or cube columns K-1 and/or middle and/or bottom and/or cube K-2 column.

In example 1, carried out according to Fig. 1, when the allocation of 1,3-butadiene from C4-faction as the extractant used N,N-dimethylacetamide with 5% water, as a desorption agent is n-hexane. Desorption agent recycle in the lower part of the column K-1. In the lower part of the column K-1 for reducing the temperature of the recycle stream of desorbed 1,3-butadiene in the amount of 1.4 t/t D2.

In example 2, implemented in accordance with Fig. 2, when the separation of isobutane-Isobutanol mixture as a separating agent used N,N-dimethylformamidine propane-propylene mixture as a separating agent used acetonitrile, as a desorption agent is n-butane. Desorption agent recycle in the lower part of the column K-2.

The data in examples 1-3, such as the composition of the main streams, their weight and the mode of the apparatus at pressures and temperatures are given in table. 1.

In example 4, implemented in accordance with Fig. 1, when the allocation of 1,3-butadiene from C4-faction as the extractant used N,N-dimethylacetamide with 5% water as a desorption agent - tert-butyl ether. Desorption agent recycle at the bottom of the columns K-1 and K-2 in a ratio of 4:1.

In example 5, implemented in accordance with Fig. 3, when the allocation of 1,3-butadiene, from C4-factions as extractant used N,N-dimethylacetamide with 5% water, as a desorption agent is a hydrocarbon, C5supplied with hydrocarbon, C4in the composition of the initial mixture F. the Quantity of hydrocarbons C5close to filed as part F, is removed as stream 7'. In Cuba column K-2 leave 3% hydrocarbon, C5that the composition of the extractant (stream 2) continue to serve in the upper part of column K-1.

Data for examples 4 and 5 are given in table. 2.

1. Method of separating hydrocarbon, C3or C4ek is n(s) hydrocarbon(s) from the extractant and recycling of the extractant in the upper part of the extractive distillation zone, characterized in that the separation less saturated hydrocarbons carried out at least in two distant areas, in Cuba, the first of which maintain the concentration of 2 - 35%, preferably 3 to 25% auxiliary desorption agent - hydrocarbon(s) and/or simple(s), ether(s), with(their) normal boiling point of 30 - 85oWith higher than target desormiere hydrocarbons, and the specified desorption agent at least partially derive from the flow of extractant followed by Stripping it from the extractant in an additional column operating at lower pressure, preferably close to atmospheric, or/and output flow target debarbieux hydrocarbons, which are then distilled off from the desorption agent.

2. The method according to p. 1, characterized in that the separated from the larger part of the extractant and the target debarbieux hydrocarbon stream containing predominantly desorption agent, return in the condensed state in the middle and/or bottom and/or cube extractive distillation column and/or the first remote areas.

3. The method according to p. 1, characterized in that when the output desorption agent with a stream of the target debarbieux hydrocarbons in the first pasture craw PP.1 - 3, characterized in that the extractant used aprotic solvents selected from the group comprising N,N-dimethylformamide, N, N-dimethylacetamide, N-organic N-formylmorpholine-methoxypropionitrile, acetonitrile or mixtures thereof with water and/or inhibitors of polymerization of hydrocarbons, and/or inhibitors of the hydrolysis of the polar solvent and corrosion.

5. The method according to PP.1 to 4, characterized in that the target deformiruemym stream is a stream containing predominantly 1,3-butadiene, and desorption agent is hydrocarbon(s) and/or ethers, C5or/and C6for example pentane or/and hexane, and/or methyl tert-butyl ether.

6. The method according to PP.1 to 5, characterized in that the desorption agent is injected into the area(s) of the distillation, and/or the bottom of the extractive distillation zone, and/or the bottom of the extractive distillation zone and/or served in the original partial hydrocarbon mixtures.

7. The method according to PP.1 - 6, characterized in that the separation of mixtures containing 1,3-butadiene, and/or PROPADIENE and/or acetylene C3- C4in the composition of the extractant enter at least nitrite(s) and/or nitrosoguanidine(I).

8. The method according to PP.1 to 7, characterized in that would primarily target desormiere hydrocarbons.

 

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